Active hyperbolic metasurfaces at telecommunication frequencies

Hyperbolic metasurfaces (HMS) combine the potential for chip-scale integration of optical metasurfaces with the properties of hyperbolic dispersion. In the ideal, lossless effective medium limit, HMS have an unbound optical density of states (DOS). The unbound DOS enables infinite mode densities in waveguides and cavities, and, in principal, an infinitely confined modal energy. The finite periodicity of real HMS, however, places an upper momentum limit on the optical DOS. Additionally, dissipation losses in real HMS limit the utility of high momentum states. To assess the possibility of reducing propagation losses in hyperbolic metamaterials, various studies have analyzed the effect of incorporating gain media. While early studies focused on using dye molecules for visible gain, more recently, indium gallium arsenide phosphide (InGaAsP) multiple quantum wells (MQW) has emerged as a viable candidate for gain at telecommunication frequencies. Herein, we report on the demonstration of active hyperbolic metasurfaces (HMS) at telecommunication frequencies. Built from nanostructured silver and InGaAsP MQW, the HMS exhibit hyperbolic dispersion across the near-infrared part of the spectrum. When driven by an external optical pump at 1064 nm, the HMS emit broadband radiation in the 1200 nm–1600nm spectral range. Extreme anisotropy of total emission with respect to the pump polarization is observed, with peak PL differing by more than an order of magnitude for orthogonal pump polarization states. Additionally, we measure degree-of-linear-polarization of the emission as high as 0.9. Experimental results are understood through analytical and numerical modeling, which illustrate the efficacy of the effective medium approximation. Finally, we report on device- and circuit-level applications of the active HMS.